Semiconductor device and a manufacturing method of the same

ABSTRACT

A semiconductor device having a structure in which the structure is laminated in many stages is made thin. A reforming area is formed by irradiating a laser beam, where a condensing point is put together with the inside of the semiconductor substrate of a semiconductor wafer. Then, after applying the binding material of liquid state to the back surface of a semiconductor wafer by a spin coating method, this is dried and a solid-like adhesive layer is formed. Then, a semiconductor wafer is divided into each semiconductor chip by making the above-mentioned reforming area into a division origin. By pasting up this semiconductor chip on the main surface of the other semiconductor chip by the adhesive layer of the back surface, a semiconductor device having a structure in which the semiconductor device is laminated in many stages is manufactured.

This application is a continuation of U.S. patent application Ser. No.12/773,231, filed May 4, 2010, which is a divisional of U.S. patentapplication Ser. No. 12/409,451, filed Mar. 23, 2009, which is acontinuation of U.S. patent application Ser. No. 11/500,945, filed Aug.9, 2006, now U.S. Pat. No. 7,514,294, the contents of which are herebyincorporated by reference into this application.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese patent applicationNo. 2005-231946 filed on Aug. 10, 2005, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to the manufacturing method of asemiconductor device, and a semiconductor device technology, andparticularly relates to the multi-stage layering technique of a chip.

DESCRIPTION OF THE BACKGROUND ART

In recent years, in connection with the size and weight reduction of themobile computing devices represented by a cellular phone, the digitalcamera, etc. and the information storage medium represented by thememory card etc., densification of the semiconductor device built intothese is advanced. The thickness reduction of the semiconductor chipwhich forms a semiconductor device is indispensable to the densificationof a semiconductor device. The multi-stage laminated constitution whichaccumulates the semiconductor chips made thin to many stages, such astwo stages, or three stages is also developed, and densification of thesemiconductor device is advanced further.

The method which laminates the semiconductor chip of the second stagevia a paste state binding material to the region inside a plurality ofelectrodes formed, for example on the main surface of the semiconductorchip of the first stage is one of the methods which paste up between thesemiconductor chips accumulated to many stages. However, by this method,according to the press load at the time of mounting the semiconductorchip of the second stage, a paste state binding material may overflowbetween up and down semiconductor chips horizontally (to a plurality ofelectrodes of the semiconductor chip of the first stage), and may coverthe electrode of the main surface of the lower semiconductor chip. Sincethe semiconductor chip is thin, the paste state binding material maycrawl up to a main surface from the back surface through the side faceof the upper semiconductor chip. Since the binding material is pastestate, in addition to the accuracy of thickness being low, thesemiconductor chip mounted on the binding material may incline.

As a method which solves such trouble, film-like adhesion members, suchas a die attach film (Die Attach Film: henceforth DAF), are developed,for example, and it contributes to the miniaturization and thicknessreduction of a semiconductor device, and multi-stage lamination of asemiconductor chip. There are Cut and Reel Method and Wafer Back SurfaceSticking Method in the adhesion method of the semiconductor chip usingDAF, for example. Cut and Reel Method is a method of transporting andsticking on the chip mounting surface of a lower semiconductor chip DAFcut to chip size, and sticking another semiconductor chip on it. On theother hand, the above-mentioned Wafer Back Surface Sticking Method is amethod of cutting the DAF simultaneously with a semiconductor chip atthe time of dicing after sticking DAF so that the whole surface of theback surface of the semiconductor wafer may be covered, and sticking thesemiconductor chip on the chip mounting surface of the lowersemiconductor chip by DAF of the back surface.

About a die-bonding technology, Japanese Unexamined Patent PublicationNo. Hei 8-236554 (Patent Reference 1) has a description, for example.The technology of obtaining the semiconductor device which equipped theback surface with the thermoplastic electrically conductive polyimidelayer, separating the wafer per chip after forming the thermoplasticelectrically conductive polyimide layer on the back surface of the waferwith a spin coat method is disclosed.

-   [Patent Reference 1] Japanese Unexamined Patent Publication No. Hei    8-236554

SUMMARY OF THE INVENTION

However, the present inventor found out that the following problemsoccurred in the multi-stage laminated constitution of the semiconductorchip using the film adhesion member of the above.

The first is a problem regarding the thickness of a film-like adhesionmember. That is, as for the thickness of a film-like adhesion member,being till about 10 μm is a limitation from the reason fortransportation or manufacture of a film-like adhesion member. Whenexplaining in detail, as for a film-like adhesion member, since adhesivelayer is formed on a film substrate, thickness of the film substratecannot be disregarded. Therefore, it is difficult to make it thin below10 μm. For this reason, there is a problem of hampering the overallthickness reduction of the multi-stage laminated constitution ofsemiconductor chips.

The second is a problem by the change of a dicing method. Since a dicingmethod cuts making the high velocity revolution of the dicing blade sothat the front surface of a wafer may be pressed, its stress applied tothe wafer is very high. That is, although thickness reduction of thesemiconductor wafer is advanced as mentioned above, there is a problemthat a chipping will occur in a semiconductor wafer when a thinsemiconductor wafer is cut by Blade Dicing Method, and the die strengthof the thin semiconductor chip falls remarkably. Although there is aproduct which uses the low dielectric constant film (the so-called Low-kfilm) whose dielectric constant is lower than a silicon oxide as awiring interlayer insulation film of a semiconductor chip from aviewpoint of improvement in the working speed of a semiconductor device,since there are cases of being easy to peel since a Low-k film is weak,and of having very small bubbles inside, it cannot be cut well by BladeDicing Method. Then, Stealth Dicing Method attracts attention as a newdicing method which avoids those problems. This Stealth Dicing Method isa dicing method which irradiates laser beam to the inside of asemiconductor wafer, forms a reforming layer selectively, and cuts thesemiconductor wafer by making the reforming layer into a divisionorigin. Since even the very thin semiconductor wafer of thickness beingabout 30 μm is cut directly according to this method, without givingstress physically, a chipping can be reduced and die strength of thesemiconductor chip is not reduced. Moreover, since high-speed dicing ofmore than or equal to 300 mm/s is possible irrelevant to the thicknessof a semiconductor wafer, a throughput can also be improved. Therefore,Stealth Dicing Method is an indispensable technology to the thicknessreduction of a semiconductor chip. However, when adopting Wafer BackSurface Sticking Method as mentioned above and Stealth Dicing Method isperformed, since the resin layer does not pass laser beam, the resinlayer itself cannot be cut, and DAF may be unable to be cut well. Forthis reason, although it is necessary to choose the resin material whichadjusted hardness and brittleness excellent in cutting as a material ofDAF, in addition to the increase of material cost in the case, thecutting surface of resin does not become uniform, and it is difficult tocut finely along a dicing line. For this reason, the yield andreliability of a semiconductor device fall. In order to make a cuttingsurface uniform, it is effective to make a resin layer thin to about 5μm or less than it, but being till about 10 μm of the thickness of DAFis a limitation as mentioned above. Therefore, there is a problem thatadoption of Stealth Dicing Method is hampered and the thicknessreduction of a semiconductor chip is hampered.

Then, a purpose of the present invention is to offer a technology whichcan make thin the semiconductor device having the structure whichlaminated chips to many stages.

The above-described and the other purposes and novel features of thepresent invention will become apparent from the description herein andaccompanying drawings.

Of the inventions disclosed in the present application, typical oneswill next be summarized briefly.

That is, the present invention has a step which forms a solid-likeadhesive layer applying a liquefied binding material to the back surfaceof a wafer by the spin coating method or the printing method, and a stepwhich performs a laser dicing process to the wafer.

The present invention is provided with the structure which stacked aplurality of chips to many stages, and its thickness of the adhesivelayer between the chips is thinner than the thickness of the adhesivelayer between the chip of the undermost layer of the chips, and thewiring substrate which mounts this.

Advantages achieved by some of the most typical aspects of the inventiondisclosed in the present application will be briefly described below.

Namely, since thickness of the adhesive layer between the chips piled upto many stages can be made thin by having a step which applies aliquefied binding material to the back surface of a wafer by the spincoating method or the printing method, and forms a solid-like adhesivelayer, and a step which performs a laser dicing process to the wafer,the semiconductor device having the structure which laminated the chipto many stages can be made thin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of the manufacturing process of a semiconductordevice which is the one embodiment of the present invention;

FIG. 2 is the whole main surface plan view of the semiconductor waferafter the preceding process of FIG. 1;

FIG. 3 is a principal part enlarged plan view of an example of thesemiconductor wafer of FIG. 2;

FIG. 4 is an enlarged plan view of region R1 of FIG. 3;

FIG. 5 is a cross-sectional view of X1-X1 line of FIG. 4;

FIG. 6 is a cross-sectional view of the semiconductor wafer in the backsurface processing step of FIG. 1;

FIG. 7 is a cross-sectional view of the semiconductor wafer in the backsurface processing step following FIG. 6;

FIG. 8 is a cross-sectional view of the semiconductor wafer in the backsurface processing step following FIG. 7;

FIG. 9 is a cross-sectional view of the semiconductor wafer at the timeof the laser irradiation step of the chip division step of FIG. 1;

FIG. 10 is a principal part enlarged plan view of the semiconductorwafer at the time of the laser irradiation step of the chip divisionstep of FIG. 1;

FIG. 11 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step of the chip division step of FIG. 1;

In FIG. 12, left-hand side is a cross-sectional view of thesemiconductor wafer at the time of the adhesive layer forming stepfollowing FIG. 11, and right-hand side is the whole back surface planview of the semiconductor wafer at the time of the adhesive layerforming step following FIG. 11;

In FIG. 13, left-hand side is a cross-sectional view of thesemiconductor wafer at the time of the adhesive layer forming stepfollowing FIG. 12, and right-hand side is the whole back surface planview of the semiconductor wafer at the time of the adhesive layerforming step following FIG. 12;

FIG. 14 is a cross-sectional view of the semiconductor wafer at the timeof the wafer mounting step of the chip division step of FIG. 1;

FIG. 15 is a cross-sectional view of the semiconductor wafer at the timeof the WSS peeling process of the chip division step of FIG. 1;

FIG. 16 is a cross-sectional view of the semiconductor wafer at the timeof the WSS peeling process of the FIG. 1 following FIG. 15;

FIG. 17 is a whole plan view of the main surface of a semiconductorwafer and the jig on which this was stuck after the wafer mounting stepof FIG. 1;

FIG. 18 is a cross-sectional view of X2-X2 line of FIG. 17;

FIG. 19 is a cross-sectional view of the semiconductor wafer at the timeof the division step of the chip division step of FIG. 1;

FIG. 20 is the whole back surface plan view of the semiconductor waferat the time of the division step of FIG. 1;

FIG. 21 is a cross-sectional view of the semiconductor wafer at the timeof the picking-up step of the assembly process of FIG. 1;

FIG. 22 is a perspective view of the semiconductor chip at the time ofthe die-bonding step of the assembly process of FIG. 1;

FIG. 23 is a cross-sectional view of the semiconductor chip at the timeof the die-bonding step of the assembly process of FIG. 1;

FIG. 24 is a cross-sectional view of the semiconductor device after thewire bonding step of the assembly process of FIG. 1;

FIG. 25 is a cross-sectional view of the semiconductor device after themolding step of the assembly process of FIG. 1;

FIG. 26 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step of the FIG. 1 in the manufacturingprocess of a semiconductor device which is an other embodiment of thepresent invention;

FIG. 27 is a plan view of the mask used at the time of the adhesivelayer forming step of FIG. 26;

FIG. 28 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step following FIG. 26;

FIG. 29 is a plan view of the back surface side of the semiconductorwafer of FIG. 28;

FIG. 30 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step following FIG. 28;

FIG. 31 is a plan view of the back surface of the semiconductor wafer ofFIG. 30;

FIG. 32 is a cross-sectional view of the semiconductor wafer at the timeof the wafer mounting step of the chip division step following FIG. 30;

FIG. 33 is a cross-sectional view of the semiconductor wafer after theWSS peeling process following FIG. 32;

FIG. 34 is a cross-sectional view of the semiconductor wafer at the timeof the division step following FIG. 33;

FIG. 35 is the whole back surface plan view of the semiconductor waferof FIG. 34;

FIG. 36 is a flow diagram of the manufacturing process of asemiconductor device which is a further other embodiment of the presentinvention;

FIG. 37 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step of the chip division step of FIG. 36;

In FIG. 38, left-hand side is a cross-sectional view of thesemiconductor wafer at the time of the adhesive layer forming step ofthe chip division step following FIG. 37, and right-hand side is thewhole semiconductor wafer plan view at this time;

In FIG. 39, left-hand side is a cross-sectional view of thesemiconductor wafer at the time of the adhesive layer forming step ofthe chip division step following FIG. 38, and right-hand side is thewhole semiconductor wafer plan view at this time;

FIG. 40 is a cross-sectional view of the semiconductor wafer at the timeof the wafer mounting step of the FIG. 36 following FIG. 39;

FIG. 41 is a cross-sectional view of the semiconductor wafer at the timeof the laser irradiation step of the FIG. 36 following FIG. 40;

FIG. 42 is a cross-sectional view of the semiconductor wafer at the timeof the WSS peeling process of the FIG. 36 following FIG. 41;

FIG. 43 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step of the FIG. 36 in the manufacturingprocess of a semiconductor device which is an other embodiment of thepresent invention;

FIG. 44 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step following FIG. 43;

FIG. 45 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step following FIG. 44;

FIG. 46 is a cross-sectional view of the semiconductor wafer at the timeof the wafer mounting step following FIG. 45;

FIG. 47 is a cross-sectional view of the semiconductor wafer at the timeof the laser irradiation step following FIG. 46;

FIG. 48 is a plan view of the mask used at the time of the adhesivelayer forming step of the manufacturing process of a semiconductordevice which is an other embodiment of the present invention;

FIG. 49 is a cross-sectional view of the semiconductor wafer at the timeof the above-mentioned adhesive layer forming step which used the maskof FIG. 48;

FIG. 50 is a cross-sectional view of the semiconductor wafer at the timeof the adhesive layer forming step following FIG. 49;

FIG. 51 is a principal part enlarged plan view of the back surface ofthe semiconductor wafer of FIG. 50;

FIG. 52 is a cross-sectional view of the semiconductor wafer at the timeof the wafer mounting step following FIG. 50;

FIG. 53 is a cross-sectional view of the semiconductor wafer after theWSS peeling process following FIG. 52;

FIG. 54 is a cross-sectional view of the semiconductor wafer at the timeof the division step following FIG. 53; and

FIGS. 55 to 58 are cross-sectional views of the semiconductor devicewhich is an other embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the below-described embodiments, a description will be made afterdivided into plural sections or in plural embodiments if necessary forconvenience sake. These plural sections or embodiments are notindependent each other, but in relation such that one is a modificationexample, details or complementary description of a part or whole of theother one unless otherwise specifically indicated. And, in thebelow-described embodiments, when a reference is made to the number ofelements (including the number, value, amount and range), the number isnot limited to a specific number but may be equal to or greater than orless than the specific number, unless otherwise specifically indicatedor principally apparent that the number is limited to the specificnumber. Further, in the below-described embodiments, it is needless tosay that the constituting elements (including element steps) are notalways essential unless otherwise specifically indicated or principallyapparent that they are essential. Similarly, in the below-describedembodiments, when a reference is made to the shape or positionalrelationship of the constituting elements, that substantially analogousor similar to it is also embraced unless otherwise specificallyindicated or principally apparent that it is not. This also applies tothe above-described value and range. And, in all the drawings fordescribing the embodiments, members of a like function will beidentified by like reference numerals and overlapping descriptions willbe omitted as much as possible. Hereafter, embodiments of the inventionare explained in detail based on drawings.

Embodiment 1

The manufacturing method of the semiconductor device of Embodiment 1 isexplained along the flow diagram of FIG. 1.

First, in preceding process 100, the semiconductor wafer (henceforth awafer) which has a main surface and a back surface which serve as theopposite side mutually along a thickness direction is prepared, and aplurality of semiconductor chips (henceforth a chip) are formed in themain surface (device formation surface) of the wafer. This precedingprocess 100 is also called a wafer process or a wafer fabrication, formsa chip (an element and a circuit) in the main surface of a wafer, and isa step until it changes into the state where an electrical test can bedone with a probe etc. There are a film formation step, an impurityintroduction (diffusion or ion implantation) step, photolithographystep, an etching step, a metallizing step, a cleaning step, a test stepbetween each step, etc. in a preceding process.

FIG. 2 shows the whole main surface plan view of wafer 1W after thispreceding process 100, FIG. 3 shows the principal part enlarged planview of an example of wafer 1W of FIG. 2, FIG. 4 shows the enlarged planview of region R1 of FIG. 3, and FIG. 5 shows the cross-sectional viewof X1-X1 line of FIG. 4.

Wafer 1W is a semiconductor thin plate of about 300 mm in diameter of analmost circle shape in plan view, for example, and a plurality of chips1C of plane quadrangular shape are arranged via cutting area (isolationregion) CR in the main surface of the perimeter in each, for example.Semiconductor substrate (henceforth a substrate) 15 of wafer 1W includesa silicon (Si) single crystal, for example, and an element and wiringlayer 1L are formed in the main surface. The thickness (total with thethickness of substrate 1S and the thickness of wiring layer 1L) of wafer1W of this phase is about 775 μm, for example. Reference N of FIG. 2shows a notch. Reference CL of FIG. 4 shows a cutting plane line.Cutting-plane-line CL is arranged so that it may pass along almost acenter of the width direction (the short direction) of cutting area CR.

In the above-mentioned wiring layer 1L, interlayer insulation film 1Liwirings, a bonding pad (external terminal; hereafter called a pad) 1LB,pad 1LBt for a test (TEG: Test Element Group), alignment target Am, andpassivation film (henceforth protective film) 1Lp are formed. Interlayerinsulation film 1Li has a plurality of interlayer insulation films 1Li1,1Li2, and 1Li3. An insulating film of an inorganic system like a siliconoxide (SiO₂ etc.) is used for interlayer insulation films 1Li1 and 1Li3,for example. A low dielectric constant film (Low-k film) like organicpolymer or organic silica glass whose dielectric constant is lower thana silicon oxide is used for interlayer insulation film 1Li2 from aviewpoint of improvement in the working speed of a semiconductor device,for example.

As this organic polymer (perfect organic system low dielectricinterlayer insulation film), there are SiLK (U.S. The Dow Chemical Comake, relative dielectric constant=2.7, heatproof temperature=490° C. ormore, and dielectric breakdown voltage=4.0-5.0 MV/Vm), FLARE of the polyallyl ether (PAE) system material (U.S. Honeywell Electronic Materialsmake, relative dielectric constant=2.8, and heatproof temperature=400°C. or more), etc., for example. This PAE system material has the featureof basic performance being high and excelling in mechanical strength,thermal stability, and low cost characteristic.

As the above-mentioned organic silica glass (SiOC system material),there are HSG-R7 (Hitachi Chemical make, relative dielectricconstant=2.8, and heatproof temperature=650° C.), Black Diamond (U.S.Applied Materials, Inc make, relative dielectric constant=3.0-2.4, andheatproof temperature=450° C.), p-MTES (Hitachi Development make,relative dielectric constant=3.2), etc., for example. As other SiOCsystem materials, there are CORAL (U.S. Novellus Systems, Inc make,relative dielectric constant=2.7-2.4, and heatproof temperature=500°C.), Aurora2.7 (ASM Japan K.K. make, relative dielectric constant=2.7,and heatproof temperature=450° C.)., etc., for example.

For example, as other low dielectric constant film materials, the SiOFsystem material of perfect organic systems, such as FSG, HSQ (hydrogensilsesquioxane) system material, MSQ (methyl silsesquioxane) systemmaterial, a porous HSQ system material, a porous MSQ material, or aporous organic system material can also be used.

As the above-mentioned HSQ system material, there are OCD T-12 (TOKYOOHKA KOGYO make, relative dielectric constant=3.4-2.9, and heatprooftemperature=450° C.), FOx (U.S. Dow Corning Corp. make, relativedielectric constant=2.9), OCL T-32 (TOKYO OHKA KOGYO make, relativedielectric constant=2.5, and heatproof temperature=450° C.) etc., forexample.

As the above-mentioned MSQ system material, there are OCD T-9 (TOKYOOHKA KOGYO make, relative dielectric constant=2.7, and heatprooftemperature=600° C.), LKD-T200 (JSR make, relative dielectricconstant=2.7-2.5, and heatproof temperature=450° C.)., HOSP (U.S.Honeywell Electronic Materials make, relative dielectric constant=2.5,and heatproof temperature=550° C.), HSG-RZ25 (Hitachi Chemical make,relative dielectric constant=2.5, and heatproof temperature=650° C.),OCL T-31 (TOKYO OHKA KOGYO make, relative dielectric constant=2.3, andheatproof temperature=500° C.), LKD-T400 (JSR make, relative dielectricconstant=2.2-2, and heatproof temperature=450° C.), etc., for example.

As the above-mentioned porous HSQ system material, there are XLK (U.S.Dow Corning Corp. make, relative dielectric constant=2.5-2), OCL T-72(TOKYO OHKA KOGYO make, relative dielectric constant=2.2-1.9, andheatproof temperature=450° C.)., Nanoglass (U.S. Honeywell ElectronicMaterials make, relative dielectric constant=2.2-1.8, heatprooftemperature=500° C. or more), or MesoELK (U.S. Air Products andChemicals, Inc, relative dielectric constant=2 or less).

As the above-mentioned porous MSQ system material, there are HSG-6211X(Hitachi Chemical make, relative dielectric constant=2.4, heatprooftemperature=650° C.), ALCAP-S (Asahi Chemical Industry make, relativedielectric constant=2.3-1.8, heatproof temperature=450° C.), OCL T-77(TOKYO OHKA KOGYO make, relative dielectric constant=2.2-1.9, heatprooftemperature=600° C.)., HSG-6210X (Hitachi Chemical make, relativedielectric constant=2.1, and heatproof temperature=650° C.) or silicaaerogel (Kobe steel make, relative dielectric constants 1.4-1.1), forexample.

As the above-mentioned porous organic system material, there is PolyELK(U.S. Air Productsand Chemicals, Inc, relative dielectric constant=2 orless, and heatproof temperature=490° C.) etc., for example.

The above-mentioned SiOC system material and SiOF system material areformed, for example by CVD method (Chemical Vapor Deposition). Forexample, above Black Diamond is formed by the CVD method which used themixed gas of trimethylsilane and oxygen. Above-mentioned p-MTES isformed by the CVD method which used the mixed gas ofmethyltriethoxysilane and N20, for example. The other above-mentionedinsulating material of the low dielectric constant is formed, forexample by the applying method.

In FIG. 5, in order to simplify explanation, the monolayer showsinterlayer insulation film 1Li2, but a plurality of low dielectricconstant films are laminated in practice. Between these low dielectricconstant films, insulating films, such as silicon carbide (SiC) andsilicon carbonitride (SiCN), intervene, for example. Between insulatingfilms, such as the silicon carbide, silicon carbonitride, etc., and alow dielectric constant film, the cap insulating film which includes forexample, silicon oxide (SiOx) represented by silicon dioxide (SiO₂) mayintervene. This cap insulating film has functions at the time of theChemical Mechanical Polishing process (CMP; Chemical MechanicalPolishing), such as reservation of mechanical strength, a surfaceprotection, moisture resistance reservation, etc. of a low dielectricconstant film, for example. The thickness of this cap insulating film isformed relatively thinly rather than the low dielectric constant film.However, a cap insulating film is not limited to a silicon oxide film,and can be changed variously, for example, a silicon nitride (SixNy)film, a silicon carbide film, or a silicon carbonitride film may be usedfor it. These silicon nitride films, a silicon carbide film, or asilicon carbonitride film can be formed, for example by plasma CVDmethod. As a silicon carbide film formed by plasma CVD method, there isBLOk (AMAT make, relative dielectric constant=4.3), for example. On theoccasion of the formation, the mixed gas of trimethylsilane and helium(or N₂, NH₃) is used, for example.

By FIG. 5, in order to simplify explanation, the wiring is not shown ininterlayer insulation film 1Li2, but actually, the above-mentionedwiring becomes a multilayer and is formed in interlayer insulation film1Li2. Let this wiring be an embedded wiring, for example. That is, thiswiring is formed by a conductor film being embedded in the wiring gutterformed in each layer of interlayer insulation film 1Li2. The conductorfilm which forms a wiring has a main conductor film, and the barriermetal film formed so that it covers the peripheral surface (a bottomface and a side face). The main conductor film includes, for examplecopper (Cu). The barrier metal film includes, for example titaniumnitride (TiN), tungsten nitride (WN), tantalum nitride (TaN), tantalum(Ta), titanium (Ti), tungsten (W), titanium tungsten (TiW), or thoselaminated films.

The wiring, pad 1LB, 1LBt, and alignment target Am on interlayerinsulation film 1Li3 includes, for example metallic films, such asaluminium. Such a wiring and pad 1LB, LBt, etc. of the uppermost arecovered by protective film 1Lp formed in the top layer of wiring layer1L. Protective film 1Lp includes for example, the laminated film of theinsulating film of an inorganic system like silicon oxide, theinsulating film of an inorganic system like a silicon nitride depositedon it, and the insulating film of an organic system like polyimide resinfurther deposited on it. Opening 2 is formed in a part of thisprotective film 1Lp, and a part of pad 1LB and 1LBt are exposed fromthere. Along the periphery of chip 1C, pad 1LB is arranged and locatedin a line, and is electrically connected with the integrated circuitdevice of chip 1C through the wiring in the above-mentioned interlayerinsulation film 1Li.

Pad 1LBt for a test and alignment target Am are arranged at cutting areaCR of chip 1C. Pad 1LBt for a test is formed in plane rectangular shape,for example, and is electrically connected with the element for TEGthrough the above-mentioned wiring. Alignment target Am is a patternused in the case of for example, the alignment of manufacturingapparatuses, such as an aligner, and chip 1C of wafer 1W, and is formedin plane cross shape, for example. Alignment target Am may be formed inthe shape of an L character and dot form other than cross shape.

In test process 101 of the continuing FIG. 1, a probe is put to pad 1LBof respective chips 1C and pad 1LBt for a test of cutting area CR ofwafer 1W, and various kinds of electrical property tests are conductedby it. This test process is also called a G/W (Good chip/Wafer) checkstep, and is an examination process which mainly judges the quality ofrespective chips 1C formed in wafer 1W electrically.

Back process 102 of the continuing FIG. 1 is a step of until it storesthe above-mentioned chip 1C to a sealing body (package) and completes,and has back surface processing step 102A, chip division step 102B, andassembly process 102C. Hereafter, back surface processing step 102A,chip division step 102B, and assembly process 102C are explained inorder.

FIG. 6-FIG. 8 show the cross-sectional view of wafer 1W in theabove-mentioned back surface processing step 102A.

First, as shown in FIG. 6, adhesive layer 3 is uniformly applied by aspin coating (spin coat) method etc. all over the main surface of wafer1W. Then, as shown in FIG. 7, supporting substrate 4 is stuck viaadhesive layer 3 on the main surface of wafer 1W (step 102A1 of FIG. 1).This supporting substrate 4 is a wafer support system (Wafer SupportSystem: WSS) which functions as a reinforcing member of wafer 1W in anext step. Hereby, at the time of transportation of wafer 1W, wafer 1Wof ultra thin and a major diameter can be handled in the state where itwas stabilized. Since wafer 1W can also be protected from an externalimpact, a crack, a chip, etc. of wafer 1W can be suppressed orprevented. Since a warp and bending of wafer 1W can be suppressed orprevented, and the flatness of wafer 1W of ultra thin and a majordiameter can be improved at the time of each next step, the stabilityand controllability of a process of each step can be improved. As amaterial of supporting substrate 4, a hard supporting substrate(Hard-WSS or Glass-WSS) like transparent glass is used, for example.However, other hard supporting substrates (Hard-WSS) like stainlesssteel may be used as other materials of supporting substrate 4, forexample. As a material of further others of supporting substrate 4, forexample, tape WSS which stuck insulated supporting substrates, such asPET (Polyethylene Terephthalate) and PEN (Polyethylene Naphthalate), onthe tape base may be used. When sticking supporting substrate 4 on themain surface of wafer 1W, supporting substrate 4 is fixed to the mainsurface of wafer 1W by pushing and attaching the formation surface ofpeeling layer 4 a of supporting substrate 4 on adhesive layer 3. Thispeeling layer 4 a is a functional layer for making peeling easy, whenpeeling supporting substrate 4 from wafer 1W.

Then, as shown in FIG. 8, after measuring the thickness of wafer 1W,based on the result of the measurement, a thickness reduction process isperformed to wafer 1W. Here, grinding processing and polishingprocessing (flat processing) are performed to the back surface of wafer1W (steps 102A2, 102A3 of FIG. 1). The thickness (total with thethickness of substrate 1S and the thickness of wiring layer 1L) of wafer1W after such a thickness reduction process is made 100 μm or less (forexample, about 90 μm, about 70 μm, or about 50 μm), for example. Whenthe thickness of wafer 1W becomes thin and becomes less than or equal to100 μm, the die strength of a chip will fall owing to the damage andstress which were generated at the back surface of wafer 1W by theabove-mentioned back surface grinding processing, and it will becomeeasy to generate the trouble that a chip will break by the pressure whenmounting the chip here. For this reason, the back surface polishingprocess after back surface grinding processing is an important processwhen losing damage and stress of the back surface of wafer 1W, so thatsuch trouble may not happen. As a back surface polishing process,besides the method of polishing using a polishing pad and silica andChemical Mechanical Polishing (CMP) method, for example, the etchingmethod using nitric acid and fluoric acid, may be used. However, whenflattening of the back surface of wafer 1W is made by the polishingprocess, impurities may be easily diffused toward wafer 1W inside(device formation surface) from the back surface of wafer 1W. Therefore,in the case of the product which needs to operate irregularity (damage,stress, etc.) of the back surface of wafer 1W as a gettering layer forimpurity capture, a back surface polishing process is not performed, butit may leave irregularity (damage, stress, etc.) intentionally to theback surface of wafer 1W. The broken line of FIG. 8 shows substrate 1Sbefore the thickness reduction process.

Next, FIG. 9 shows the cross-sectional view of wafer 1W at the time oflaser irradiation step 102B1 of chip division step 102B, and FIG. 10shows the principal part enlarged plan view of wafer 1W of FIG. 9.

First, ultra thin wafer 1W is transported while sticking supportingsubstrate 4 on the main surface to a laser dicing apparatus, and wherethe back surface of the wafer 1W is turned upwards, it is laid on achuck. Then, the patterns (pad 1LBt and alignment target Am arranged atcutting area CR, pad 1LB arranged in chip 1C, etc. besides the patternof chip 1C or cutting area CR) of the main surface of wafer 1W arerecognized from the back surface of wafer 1W using an infrared camera(henceforth, IR camera). Then, after carrying out alignment (locationamendment) of cutting-plane-line CL based on the pattern informationacquired with IR camera, while irradiating laser beam (energy beam) LB1emitted from laser generating part 5 from the back surface side of wafer1W where a condensing point is put together with the inside of substrate1S of wafer 1W, it is made to move along cutting-plane-line CL by whichalignment was made based on the above-mentioned pattern information.This forms reforming area (optical damaged part or crushing layer) PL bymultiple photon absorption in the inside of substrate 1S in cutting areaCR of wafer 1W. This reforming area PL is formed by the inside of wafer1W having been heated and melted by multiple photon absorption, andserves as a cutting origin region of wafer 1W at the time of a laterchip division step. This melting treatment region is the regionre-solidified after once melting, a region of a just molten state, and aregion in the state of re-solidifying from a molten state, and can alsobe called the region which made the change of phase, and region wherethe crystal structure changed. As for a melting treatment region, it canalso be called the region where a certain structure changed to anotherstructure in single-crystal structure, amorphous structure, andpolycrystalline structure. For example, substrate 1S portion means theregion which changed from single-crystal structure to amorphousstructure, the region which changed from single-crystal structure topolycrystalline structure, and the region which changed fromsingle-crystal structure to the structure comprising amorphous structureand polycrystalline structure.

Along cutting area CR, laser beam LB1 may be irradiated continuously andmay be irradiated intermittently. When laser beam LB1 is irradiatedcontinuously, reforming area PL is formed in the shape of a straightline along cutting-plane-line CL. When laser beam LB1 is irradiatedintermittently, reforming area PL is formed in the shape of a brokenline (dot form). Although the above-mentioned low dielectric constantfilm may discolor with the heat at the time of irradiation of laser beamLB1 since the heat conductivity is low and it is easily filled withheat, since an irradiation area of laser beam LB1 can be made small andthe generation of the heat by irradiation of laser beam LB1 can besuppressed as much as possible when laser beam LB1 is irradiatedintermittently, discoloration of the low dielectric constant film byheat can be suppressed or prevented.

Since the back surface of wafer 1W is a plane of incidence of laser beamLB1, in order to reduce or prevent diffusion of laser beam LB1, it ispreferred that it is flat and a glide plane. In formation of reformingarea PL, since laser beam LB1 is hardly absorbed with the back surfaceof wafer 1W, the back surface of wafer 1W does not melt. Although notlimited in particular, the irradiation conditions of laser beam LB1 areas follows, for example. Namely, the kind of laser beam LB1 is LDexcitation solid pulsed laser, for example, an illuminant is a YAG laserwhose wave length is 1064 nm, for example, a frequency is 400 kHz, forexample, laser power is less than or equal to 1 W, for example, thediameter of laser spot is 1-2 μm, for example, and the traveling speedof laser beam LB1 is about 300 mm/s, for example.

Next, FIG. 11-FIG. 13 show the appearance of wafer 1W at the time ofadhesive layer forming step 102B2 of chip division step 102B. FIG. 11shows the cross-sectional view of wafer 1W, the left-hand side of FIG.12 and FIG. 13 shows the cross-sectional view of wafer 1W, andright-hand side shows the whole back surface plan view of wafer 1W,respectively.

First, wafer 1W picked out from the above-mentioned laser dicingapparatus is transported while sticking supporting substrate 4 on themain surface to a spin coating apparatus (spin coater), where the backsurface of the wafer 1W is turned upwards, it is laid on a rotationsupport base, and it is fixed by making vacuum adsorption. Then, asshown in FIG. 11, binding material 8 of liquid state (paste state) isdropped in the center on the back surface of wafer 1W from nozzle 7 of aspin coating apparatus. The base material of this binding material 8includes, for example thermoplastic resin. As an example ofthermoplastic resin, there is polyimide resin, for example.Thermosetting resin may be used as base material of binding material 8,for example. As an example of thermosetting resin, there is an epoxyresin, polyimide resin, or silicone resin, for example. Then, as shownin FIG. 12, the coat of thin binding material 8 is formed all over theback surface of wafer 1W by making the high velocity revolution of thewafer 1W (spin coating method). Then, wafer 1W is transported whilesticking supporting substrate 4 on the main surface on a heat stage, adrying process is performed on the conditions for 100-200° C. and about30 minutes, for example and binding material 8 is solidified. When thebase material of binding material 8 is thermosetting resin,thermosetting resin is cured to some extent by a heat treatment, but itis not made to harden thoroughly but limits to the state of havingadhesive property. Thus, as shown in FIG. 13, thin solid-like adhesivelayer 8 a is formed all over the back surface of wafer 1W. Adhesivelayer 8 a obtained by solidifying this binding material 8 is becausechip 1C obtained from wafer 1W is fixed on an other chip at the nextstep, and it is formed all over the back surface of wafer 1W so that thethickness may become uniform. The thickness of adhesive layer 8 a isthinner than 10 μm, for example, is about 5 μm or less than it, forexample. Since adhesive layer 8 a is formed by solidifying after makingspin coating of the binding material 8 only as mentioned above, by thepart which does not need a film substrate like DAF, it is possible toform the thickness of adhesive layer 8 a more thinly than DAF.

Embodiment 1 explained how to form the coat of thin binding material 8all over the back surface of wafer 1W by making the high velocityrevolution of the wafer 1W, after binding material 8 of liquid state(paste state) is dropped in the center on the back surface of wafer 1Wfrom nozzle 7 of a spin coating apparatus. However, in using what hasthe high viscosity of adhesives 8, it is preferred for binding material8 of liquid state (paste state) to be dropped in the center on the backsurface of wafer 1W, where the high velocity revolution of the wafer 1Wis made beforehand, and to change an engine speed after that, and toform the coat of thin binding material 8 all over the back surface ofwafer 1W.

In Embodiment 1, thickness of adhesive layer 8 a can be made thin asmentioned above by forming adhesive layer 8 a using a spin coatingmethod as mentioned above. Since adhesive layer 8 a is formed with aresin coating method, the homogeneity of the thickness of adhesive layer8 a in the back surface of wafer 1W can be improved. Since the spincoating of the adhesives 8 can be carried out in the state where theflatness of wafer 1W is high, by sticking supporting substrate 4 on themain surface of wafer 1W, the homogeneity of the thickness of adhesivelayer 8 a in the back surface of wafer 1W can be improved. When notusing above WSS, when sticking only a tape material on the main surfaceof wafer 1W, or when using the above-mentioned tape WSS, it is preferredto make spin coating of the binding material 8, where vacuum suction ofthe whole surface of the main surface of wafer 1W is made to theabove-mentioned rotation support base side. Thus, since reduction orprevention of warp and bending of wafer 1W which is ultra thin and amajor diameter can be done, and the flatness of wafer 1W can be improvedby making vacuum suction of the whole surface of the main surface ofwafer 1W, the homogeneity of the thickness of adhesive layer 8 a in theback surface of wafer 1W can be improved.

When DAF is used, a specification changes with sizes, thickness, etc. ofwafer 1W, but in the case of a resin coating method like Embodiment 1, aresin material is good at one kind, and does not depend in particular onthe size or thickness of wafer 1W. Since molding technology andprocessing technology for which DAF is asked are unnecessary, cost canbe reduced. When adhering DAF on wafer 1W, in order to lose the wrinkleand void between wafer 1W and DAF and to raise adhesion, the applicationof pressure to wafer 1W is required, but with thin wafer 1W less than orequal to 50 μm, we are anxious about the damage to wafer 1W byapplication of pressure increasingly. On the other hand, in Embodiment1, in formation of adhesive layer 8 a, the application of pressure towafer 1W is unnecessary, and damage degradation of wafer 1W can bereduced or prevented. Therefore, the yield and reliability of asemiconductor device can be improved.

Next, FIG. 14 shows the cross-sectional view of wafer 1W after wafermounting step 102B3 of chip division step 102B.

At this step, as shown in FIG. 14, where supporting substrate 4 is stuckon the main surface of wafer 1W, the back surface (formation surface ofadhesive layer 8 a) of wafer 1W is stuck on tape 10 a of jig 10. Thetape base of tape 10 a of jig 10 includes a plastic material which hasflexibility, for example, and the adhesive layer is formed in the mainsurface. Wafer 1W is being firmly fixed by the adhesive layer of tape 10a. As this tape 10 a, it is also preferred to use a UV tape, forexample. A UV tape is an adhesive tape with which ultraviolet-rays (UV)hardening resin was used as a material of an adhesive layer, and has acharacteristic in which the adhesion of an adhesive layer will becomeweak when ultraviolet rays are irradiated rapidly, having powerfuladhesion. Ring 10 b is stuck on the main surface periphery of tape 10 aby the adhesive layer of tape 10 a. This ring 10 b is a reinforcingmember of tape 10 a. Although forming with metal, such as stainlesssteel, is preferred as for the viewpoint of this reinforcement to ring10 b, it may be formed with the plastic material which set up thicknessso that it has hardness comparable as metal.

Next, FIG. 15-FIG. 18 show the appearance of wafer 1W at the time of WSSpeeling process 102B4 of chip division step 102B. FIG. 15 and FIG. 16show the cross-sectional view of wafer 1W, FIG. 17 shows the whole mainsurface plan view of wafer 1W, and FIG. 18 shows the cross-sectionalview of X2-X2 line of FIG. 17, respectively.

At this step, first, as shown in FIG. 15, where a focus is put inadhesive layer 3 on the main surface of wafer 1W, laser beam LB2 emittedfrom laser generating part 11 is scanned and irradiated from one end tothe other end of the main surface of wafer 1W via transparent supportingsubstrate 4. The conditions of this laser beam LB2 are infrared laserwith a wave length of 1064 nm, output: 20 W, irradiation rate: 2000mm/s, and spot diameter: about f200 μm, for example. This peelssupporting substrate 4 from the main surface of wafer 1W, as shown inFIG. 16.

Adhesive layer 3 may includes, for example ultraviolet curing resin (UVresin). Having powerful adhesion, UV resin has a characteristic in whichcure is promoted and adhesion becomes weak rapidly, when ultravioletrays are irradiated. When UV resin is used, as for the above-mentionedlaser beam LB2, ultraviolet laser is used instead of infrared laser.Hereby, since the adhesion of adhesive layer 3 can be weakened,supporting substrate 4 can be peeled easily. Then, as shown in FIG. 17and FIG. 18, adhesive layer 3 on the main surface of wafer 1W isremoved.

Next, FIG. 19 and FIG. 20 show the cross-sectional view of wafer 1W andthe whole back surface plan view of wafer 1W at the time of divisionstep 102B5. Although FIG. 20 was a plan view, in order to make a drawinglegible, hatching was given to the formation area of adhesive layer 8 a.

At this step, as shown in FIG. 19, after putting jig 10 which mountedwafer 1W on mounting base 12, where ring 10 b of jig 10 is fixed,mounting base 12 is pushed up in the direction (direction shown by arrowA) vertical to the main surface of wafer 1W. Then, as a result of tape's10 a being extended to the diametral direction (direction shown by arrowB) of wafer 1W, a crack enters along the thickness direction of wafer 1Wby the force in which the tape 10 a is prolonged, by making reformingarea PL of wafer 1W into a division origin. This divides wafer 1W intoeach chip (second chip) 1C (stealth dicing). Adhesive layer 8 a alsobreaks between each chips 1C by division of chip 1C simultaneously. WhenDAF material is used as an adhesive layer of the back surface of chip1C, in cutting of chip 1C by stealth dicing, there is a case that theDAF material of the back surface of chip 1C cannot be cut well, such asthe case that the peripheral part of the DAF material of the backsurface of chip 1C extends without cutting. On the other hand, inEmbodiment 1, since the thickness of adhesive layer 8 a is very thincompared with DAF material as mentioned above, adhesive layer 8 a can bewell cut finely at the time of division of chip 1C by stealth dicing.Therefore, since stealth dicing is employable, it can correspond to thethickness reduction of chip 1C, and a semiconductor device can be madethin. Since the external appearance failure of chip 1C can be reduced,the yield of a semiconductor device can be improved.

Since it will become easy to generate a chipping at the time of cutting,and the die strength of a chip will fall when wafer 1W becomes thin inthe case of the Blade Dicing Method which cuts wafer 1W by a dicingblade, it is forced to process from a viewpoint of securing the qualityof chip 1C, at a low speed (for example, about 60 mm/s, or less than itdepending on the thickness of wafer 1W). On the other hand, since in thecase of Embodiment 1 damage is not done to the front surface of wafer 1Wbut splitting only of the inside is made, the chipping which exists inthe front surface of chip 1C can be suppressed to the minimum. For thisreason, the die strength of chip 1C can be improved. Since cuttingprocessing as high-speed as 300 mm/s, for example can be performed, athroughput can be improved.

As mentioned above, when irradiating a laser beam from the main surfaceside of wafer 1W, pad 1LBt for a test may become obstructive, andprocessing of the portion (formation of a reforming layer) may not beable to be performed well at cutting area CR of the main surface ofwafer 1W. On the other hand, in Embodiment 1, since laser beam LB isirradiated from the back surface side of wafer 1W in which metals, suchas pad 1LBt for a test, do not exist, reforming area PL can be formedgood, without generating the above trouble, and wafer 1W can be cutgood.

Next, FIG. 21 shows the cross-sectional view of wafer 1W at the time ofpicking-up step 102C1 of assembly process 102C. At this step, jig 10holding a plurality of chips 1C is transported to a pickup device andmounted on mounting base 15. Then, where vacuum suction of the backsurface of tape 10 a of jig 10 is made, chip 1C is pushed up from theback surface of tape 10 a by a push-up pin. When the above-mentioned UVtape is used as tape 10 a at this time, by irradiating ultraviolet raysto the adhesive layer of tape 10 a, an adhesive layer is cured andadhesive strength is weakened. In this state, vacuum suction of the chip1C is made with the collet of a pickup device, and it is pulled up.

Next, FIG. 22 shows the perspective view of chip 1C and wiring substrate17 at the time of die-bonding step 102C2 of assembly process 102C, andFIG. 23 shows the cross-sectional view of chip 1C and wiring substrate17 at the time of the step of FIG. 22. At this step, chip 1C which waspicked up as mentioned above is transported on the main surface of otherchips (first chip) 18C mounted on the main surface of wiring substrate17, as shown in FIG. 22 and FIG. 23. Then, chip 1C is descended in thestate where adhesive layer 8 a of the back surface of chip 1C and themain surface of chip 18C were made to face, and it is put on the mainsurface of chip 18C. Then, when the base material of adhesive layer 8 ais thermoplastic resin, chip 1C is adhered on the main surface of chip18C by being in the state which heats adhesive layer 8 a, made itsoften, and gave adhesive property, and pushing and attaching lightlyadhesive layer 8 a of the back surface of chip 1C on the main surface ofchip 18C. Although the heating temperature in particular at this time isnot limited, it is about 400° C. On the other hand, when the basematerial of adhesive layer 8 a is thermosetting resin, adhesive layer 8a is hardened thoroughly being applied heat, and chip 1C is adhered onthe main surface of chip 18C. Thus, chip 1C is piled up on chip 18C.

Thus, in Embodiment 1, since thickness of adhesive layer 8 a of the backsurface of chip 1C can be made thin in addition to the thicknessreduction of chip 1C, the lamination height of chips 1C and 18C can bemade low. Therefore, the semiconductor device having the structure whichlaminated chips 1C and 18C can be made thin. Since the absorbed amountof the moisture can also be reduced since adhesive layer 8 a is thin,and the generation of void can also be reduced, the reliability of asemiconductor device can also be improved. The problem that adhesivelayer 8 a covers the pad of lower chip 18C is not generated, eitherwithout overflowing into the periphery of chip 1C at the time ofmounting of chip 1C, since adhesive layer 8 a is made into solid state.Adhesive layer 8 a of the back surface of chip 1C does not crawl up to amain surface through the side face of chip 1C, even if chip 1C is thin.In addition to that the thickness accuracy of adhesive layer 8 a ishigh, the upper chip 1C does not incline. Chip 1C which was picked up isaccommodated in a transportation tray, transportation shipment to othermanufacturing factories (for example, assembly fabricator) may be madeand the assembly after this step may be requested (step 103A of FIG. 1).

Here, an example of the structure and the mounting method of wiringsubstrate 17 and chip 18C is explained. Wiring substrate 17 includes aprinted-circuit board which has multilayer interconnection structure,for example, and has the main surface and back surface which become theopposite side mutually along a thickness direction. Chip 18C is mountedon the main surface of wiring substrate 17. A plurality of electrodes 17a are arranged on the main surface of wiring substrate 17 so that theperiphery of chip 18C may be surrounded. On the back surface of wiringsubstrate 17, a plurality of electrodes 17 b are arranged. Electrode 17a of a main surface and electrode 17 b of the back surface of wiringsubstrate 17 are electrically connected through the wiring of the innerlayer of wiring substrate 17. Electrodes 17 a and 17 b and a wiring ofwiring substrate 17 include copper, for example. Gold (Au) plating ofnickel (Ni) foundation is performed to the exposed surface of electrodes17 a and 17 b.

The structure of chip 18C is almost the same as the above-mentioned chip1C. Substrate 18S of chip 18C includes a silicon (Si) single crystal,for example, and the element and wiring layer 18L are formed in the mainsurface. The structure of wiring layer 18L is the same as wiring layer1L of the above-mentioned chip 1C, and pad 18LB is arranged at the toplayer. Chip 18C is mounted on the main surface of wiring substrate 17 inthe state of turning the main surface upwards and adhering the backsurface to the main surface of wiring substrate 17 by adhesive layer 20a. Adhesive layer 20 a includes, for example thermoplastic resin likepolyimide resin. The thickness of adhesive layer 20 a is thicker thanadhesive layer 8 a of the back surface of the above-mentioned chip 1C,for example, is more than or equal to 10 μm. The reason is for makingadhesive layer 20 a absorb the big irregularity by the wiring andelectrode which were formed on the main surface of wiring substrate 17.When semiconductor chip 18C of the first stage is mounted via adhesivelayer 8 a formed with the resin coating method, since the thickness ofadhesive layer 8 a is thin such as about 5 μm, the irregularity formedon the main surface of wiring substrate 17 cannot be absorbed byadhesive layer 8 a. That is, a clearance may generate between the mainsurface of wiring substrate 17, and adhesive layer 8 a, and the problemof the void failure that sealing resin becomes non-filling may occur ina later sealing body forming step. As opposed to this, irregularity ofthe back surface of chip 1C is about 1-2 μm (MAX), for example, andirregularity of the main surface of chip 18C on which chip 1C islaminated is about 1-2 μm (MAX), for example, so that since there is noirregularity like the main surface of wiring substrate 17, it issatisfactory even if adhesive layer 8 a of the back surface of chip 1Cis made thin.

The mounting method of such a chip 18C is as follows, for example.First, wiring substrate 17 is prepared and a paste state bindingmaterial is applied to the chip mounting region of the main surface.This paste state binding material includes, for example thermoplasticresin, such as polyimide resin. Then, after pushing and attaching theback surface of chip 18C on the paste state binding material andmounting chip 18C on the main surface of wiring substrate 17, a pastestate binding material is dried and solid-like adhesive layer 20 a isformed. This adheres chip 18C to wiring substrate 17.

As shown in FIG. 58, DAF (Die Attach Film) may be used as a material ofadhesive layer 20 a. That is, semiconductor chip 18C of the first stagemay be mounted on the main surface of wiring substrate 17 via DAF(adhesive layer 20 a), and the semiconductor chip after the second stagemounted on the main surface of the semiconductor chip of the first stagemay be mounted via adhesive layer 8 a formed with the resin coatingmethod. Since DAF (adhesive layer 20 a) used for semiconductor chip 18Cof the first stage is made into solid state by this, it does notoverflow into the periphery of semiconductor chip 18C at the time ofmounting of semiconductor chip 18C. That is, since a binding material(adhesive layer 20 a) does not overflow toward electrode 17 a arrangedon the main surface of a wiring substrate, distance betweensemiconductor chip 18C and electrode 17 a can be shortened, and theminiaturization of a semiconductor device can be realized compared withthe case where a paste state binding material is used.

Next, FIG. 24 shows the cross-sectional view of the semiconductor deviceafter wire bonding step 102C3 of assembly process 102C, and FIG. 25shows the cross-sectional view of the semiconductor device after moldingstep 102C4 of assembly process 102C.

First, in wire bonding step 102C3, as shown in FIG. 24, while connectingpad 1LB of the upper chip 1C, and pad 18LB of lower layer chip 18C bybonding wire (henceforth a wire) 21, pad 18LB of lower layer chip 18Cand electrode 17 a of wiring substrate 17 are connected with wire 21.Pad 1LB of the upper chip 1C and electrode 17 a of wiring substrate 17may be connected with wire 21. Wire 21 includes, for example gold (Au).Then, in molding step 102C4, as shown in FIG. 25, chips 1C and 18C, wire21, etc. are sealed by sealing body 22 which includes epoxy system resinetc., for example using the transfer mold method. Solder ball 23 isformed as an external terminal on electrode 17 b. Solder ball 23includes the lead solder material of lead (Pb)-tin (Sn), or the leadfree solder material of for example, tin (Sn)-silver (Ag)-copper (Cu)system, for example. A semiconductor device is manufactured as mentionedabove.

Embodiment 2

In Embodiment 2, like the Embodiment 1, after passing through laserirradiation step 102B1 from preceding process 100 of FIG. 1, in adhesivelayer forming step 102B2 of chip division step 102B, an adhesive layeris formed on the back surface of a wafer by the printing method.

FIG. 26 shows the cross-sectional view of wafer 1W at the time of theabove-mentioned adhesive layer forming step 102B2, and FIG. 27 shows theplan view of mask 25A used at the time of the above-mentioned adhesivelayer forming step 102B2. Although FIG. 27 was a plan view, in order tomake a drawing legible, hatching was given to mask 25A.

First, on the back surface of wafer 1W, as shown in FIG. 26, afterputting mask 25A where alignment is made, squeegee 26 extends bindingmaterial 8 of liquid state (paste state) along the back surface of wafer1W from on this mask 25A. In mask 25A, as shown in FIG. 26 and FIG. 27,opening 25A1 of the almost same plane size as each chip 1C is formed inthe correspondence location of each chip 1C of wafer 1W, and the backsurface of each chip 1C is exposed to it from each of the opening 25A1.In mask 25A, mask pattern 25A2 is formed in the correspondence locationof cutting area CR (formation area of reforming area PL) betweencontiguity of each chip 1C of wafer 1W, and, hereby, the portioncorresponding to cutting area CR between contiguity of chip 1C iscovered.

Next, FIG. 28 shows the cross-sectional view of wafer 1W showing a statethat squeegee 26 extended binding material 8 of liquid state, and it isapplied to the back surface of wafer 1W selectively via mask 25A, andFIG. 29 shows the plan view of the back surface side of wafer 1W of FIG.28. Although FIG. 29 was a plan view, in order to make a drawinglegible, hatching was given to the coating region of binding material 8.In FIG. 29, in order to make a drawing legible, wafer 1W is shownlooking through.

As shown in FIG. 28 and FIG. 29, when squeegee 26 is moved extendingbinding material 8 along the back surface of wafer 1W, binding material8 of liquid state will enter in opening 25A1 of mask 25A. Hereby,although binding material 8 adheres to the back surface of chip 1C, itdoes not adhere to cutting area CR. Thus, squeegee 26 is moved from oneend to the other end of wafer 1W.

Next, FIG. 30 shows the cross-sectional view of wafer 1W showing thestate where mask 25A was removed, and FIG. 31 shows the plan view of theback surface of wafer 1W of FIG. 30. Although FIG. 31 was a plan view,in order to make a drawing legible, hatching was given to the coatingregion of binding material 8 (adhesive layer 8 b).

After applying binding material 8 to the back surface of wafer 1W,solid-like adhesive layer 8 b is selectively formed in the region ofrespective chips 1C of the back surface of wafer 1W by removing mask 25Aand drying binding material 8 like the Embodiment 1. Adhesive layer 8 bis not formed in cutting area CR.

Next, FIG. 32 shows the cross-sectional view of wafer 1W at the time ofwafer mounting step 102B3 of chip division step 102B, and FIG. 33 showsthe cross-sectional view of wafer 1W after WSS peeling process 102B4.

At this step, as shown in FIG. 32, like the Embodiment 1, after stickingthe back surface (formation surface of adhesive layer 8 b) of wafer 1Won tape 10 a of jig 10, as shown in FIG. 33, supporting substrate 4 ispeeled, then adhesive layer 3 is removed like the Embodiment 1.

Next, FIG. 34 and FIG. 35 show the cross-sectional view of wafer 1W andthe whole back surface plan view of wafer 1W at the time of divisionstep 102B5. Although FIG. 35 was a plan view, in order to make a drawinglegible, hatching was given to the formation area of adhesive layer 8 b.

At this step, as shown in FIG. 34 and FIG. 35, wafer 1W is divided intoeach chip (second chip) 1C like the Embodiment 1 by making reformingarea PL of wafer 1W into a division origin (stealth dicing). At thistime, in Embodiment 2, since adhesive layer 8 b is already divided intoevery each chip 1C before division step 102B5, and adhesive layer 8 b isnot formed at cutting area CR, adhesive layer 8 b between chips 1C isfinely separable. That is, stealth dicing can divide chip 1C finely,without generating trouble in the peripheral part of adhesive layer 8 bof the back surface of chip 1C. Therefore, since stealth dicing isemployable, a semiconductor device can be made thin. Since the externalappearance failure of chip 1C can be reduced, the yield of asemiconductor device can be improved. The same effect as the Embodiment1 can be acquired except this.

Since assembly process 102C after this is the same as the Embodiment 1,explanation is omitted.

Embodiment 3

The Embodiment 1 and 2 explained the case where an adhesive layer wasformed on the back surface of wafer 1W, after the laser irradiation stepfor forming reforming area LB in the chip division step. Embodiment 3explains the case where the laser irradiation step for forming reformingarea LB is performed in a chip division step after forming an adhesivelayer on the back surface of wafer 1W.

FIG. 36 shows the flow diagram of the semiconductor device of Embodiment3. In Embodiment 3, like the Embodiment 1, after passing throughpreceding process 200 and test process 201 of FIG. 36, wearing step ofWSS 202A1, back surface grinding step 202A2, and back surface polishingstep 202A3 of back surface processing step 202A of back process 202 areperformed in order.

Then, in Embodiment 3, in chip division step 202B, before performing thelaser irradiation step for forming reforming area PL, adhesive layerforming step 202B1 is performed. FIG. 37-FIG. 39 show appearance ofwafer 1W at the time of adhesive layer forming step 202B1 of chipdivision step 202B. FIG. 37 shows the cross-sectional view of wafer 1W,the left-hand side of FIG. 38 and FIG. 39 shows the cross-sectional viewof wafer 1W, and right-hand side shows the whole back surface plan viewof wafer 1W, respectively. Although the right-hand side of FIG. 38 andFIG. 39 was a plan view, in order to make a drawing legible, hatchingwas given to binding material 8 (adhesive layer 8 a).

Here, as shown in FIG. 37, like the Embodiment 1, after binding material8 of liquid state (paste state) is dropped in the center on the backsurface of wafer 1W from nozzle 7 of a spin coating apparatus, as shownin FIG. 38, the thin coat of binding material 8 is formed all over theback surface of wafer 1W by making the high velocity revolution of thewafer 1W (spin coating method). Then, like the Embodiment 1, a dryingprocess is performed to binding material 8 of the back surface of wafer1W, binding material 8 is solidified, and as shown in FIG. 39, thinsolid-like adhesive layer 8 a is formed all over the back surface ofwafer 1W. Hereby, like the Embodiment 1, thin adhesive layer 8 a can beformed on the back surface of wafer 1W so that thickness may becomeuniform.

Next, FIG. 40 shows the cross-sectional view of wafer 1W at the time ofwafer mounting step 202B2 of FIG. 36, FIG. 41 shows the cross-sectionalview of wafer 1W at the time of laser irradiation step 202B3 of FIG. 36,and FIG. 42 shows the cross-sectional view of wafer 1W at the time ofWSS peeling process 202B4 of FIG. 36, respectively.

First, as shown in FIG. 40, like the Embodiment 1, the back surface(formation surface of adhesive layer 8 a) of wafer 1W is stuck on tape10 a of jig 10, and wafer 1W is mounted on jig 10. Then, wafer 1W istransported while being mounted on jig 10 to a laser dicing apparatus,and where the main surface (namely, upper surface of supportingsubstrate 4) of the wafer 1W is turned upwards, it is laid on a chuck.Then, after recognizing patterns (except the pattern of chip 1C orcutting area CR, pad 1LBt and alignment target Am which are arranged atcutting area CR, pad 1LB arranged in chip 1C, etc.) of the main surfaceof wafer 1W from the upper part of the main surface of wafer 1W using IRcamera, based on the pattern information thereby acquired, alignment(location amendment) of cutting-plane-line CL is carried out.

Then, as shown in FIG. 41, while irradiating laser beam LB1 emitted fromlaser generating part 5 located in the main surface upper part of wafer1W from the main surface side of wafer 1W where a condensing point isput together with the inside of substrate 1S of wafer 1W via transparentsupporting substrate 4, it is made to move along cutting-plane-line CLto which alignment was made based on the above-mentioned patterninformation. This forms above-mentioned reforming area PL in the insideof substrate 1S in cutting area CR of wafer 1W. The method of a scan andirradiation conditions of laser beam LB1 are as the same as theEmbodiment 1 explained.

Then, as shown in FIG. 42, laser beam LB2 emitted from laser generatingpart 11 is scanned from one end to the other end of the main surface ofwafer 1W via transparent supporting substrate 4, and adhesive layer 3 onthe main surface of wafer 1W is irradiated. Hereby, the adhesivestrength of adhesive layer 3 is reduced and supporting substrate 4 ispeeled from wafer 1W like the Embodiment 1. Then, adhesive layer 3 onthe main surface of wafer 1W is removed like the Embodiment 1.

Since division step 202B5, assembly process 202C (picking-up step 202C1,die-bonding step 202C2, wire bonding step 202C3, molding step 202C4),and transportation shipment step 203A after this are the same as eachstep explained by the Embodiment 1, explanation is omitted.

Embodiment 4

In Embodiment 4, like the Embodiment 3, after passing through precedingprocess 200 to back surface polishing process 202A3 of FIG. 36, inadhesive layer forming step 202B1 of chip division step 202B, anadhesive layer is formed on the back surface of wafer 1W by the printingmethod.

FIG. 43 shows the cross-sectional view of wafer 1W at the time of theabove-mentioned adhesive layer forming step 202B1. FIG. 44 shows thecross-sectional view of wafer 1W in which a state that squeegee 26extended binding material 8 of liquid state, and it has applied to theback surface of wafer 1W selectively via mask 25A is shown, and FIG. 45shows the cross-sectional view of wafer 1W in which the state where mask25A was removed is shown, respectively.

First, like the Embodiment 2, as shown in FIG. 43, after putting mask25A on the back surface of wafer 1W where alignment is made, squeegee 26extends binding material 8 of liquid state (paste state) along the backsurface of wafer 1W from on this mask 25A. Then, as shown in FIG. 44,like the Embodiment 2, it enters in opening 25A2 of mask 25A, andbinding material 8 of liquid state adheres to the back surface of wafer1W. Thus, after applying binding material 8 to the back surface of wafer1W selectively, as shown in FIG. 45, mask 25A is removed like theEmbodiment 2. Then, solid-like adhesive layer 8 b is selectively formedin the region of chip 1C of the back surface of wafer 1W by dryingbinding material 8 like the Embodiment 1 and 2. Adhesive layer 8 b isnot formed in cutting area CR.

Next, FIG. 46 shows the cross-sectional view of wafer 1W at the time ofwafer mounting step 202B2 of chip division step 202B, and FIG. 47 showsthe cross-sectional view of wafer 1W at the time of laser irradiationstep 202B3 of FIG. 36, respectively.

First, like the Embodiments 1-3, as shown in FIG. 46, after sticking theback surface (formation surface of adhesive layer 8 b) of wafer 1W ontape 10 a of jig 10, the above-mentioned pattern of the main surface ofwafer 1W is recognized from the main surface upper part of wafer 1W likethe Embodiment 3 using IR camera. And based on the pattern informationthereby acquired, alignment (location amendment) of cutting-plane-lineCL is carried out. Then, as shown in FIG. 47, like the Embodiment 3,while irradiating laser beam LB1 emitted from laser generating part 5established in the main surface upper part of wafer 1W from the mainsurface side of wafer 1W where a condensing point is put together withthe inside of substrate 1S of wafer 1W via transparent supportingsubstrate 4, it is made to move along cutting-plane-line CL to whichalignment was made based on the above-mentioned pattern information.This forms above-mentioned reforming area PL in the inside of substrate15 in cutting area CR of wafer 1W.

Then, like the Embodiment 3, after peeling supporting substrate 4 fromthe main surface of wafer 1W, adhesive layer 3 on the main surface ofwafer 1W is removed, and wafer 1W is divided into each chip 1C like theEmbodiments 1-3. Since the step after this is the same as the Embodiment3, explanation is omitted.

Embodiment 5

Embodiment 5 explains the modification in the case of forming anadhesive layer in the back surface of a wafer by the printing method.

FIG. 48 shows the plan view of mask 25B used at the time of the adhesivelayer forming step of Embodiment 5. Although FIG. 48 was a plan view,hatching was attached in order to make a drawing legible.

Let the mask pattern of transcriptional region D of mask 25B be a meshshape fine pattern in Embodiment 5. That is, a plurality of openingssmaller than the plane size of chip 1C are arranged in the state whereit adjoined in the direction of four directions, in the surface oftranscriptional region D in transcriptional region D of mask 25B.

Next, FIG. 49 shows the cross-sectional view of wafer 1W at the time ofthe above-mentioned adhesive layer forming step 102B2, FIG. 50 shows thecross-sectional view of wafer 1W in which the state where mask 25B wasremoved is shown, and FIG. 51 shows the principal part enlarged planview of the back surface of wafer 1W of FIG. 50, respectively. AlthoughFIG. 51 was a plan view, in order to make a drawing legible, hatchingwas given to adhesive layer 8 b.

First, as shown in FIG. 49, like the Embodiment 2, after putting mask25B shown in FIG. 48 on the back surface of wafer 1W where alignment ismade, binding material 8 of liquid state (paste state) is selectivelyapplied to the back surface of wafer 1W through opening 25B1 of mask25B, being extended along the back surface of wafer 1W from on mask 25Bby squeegee 26. At this time, binding material 8 is not applied to thelocation corresponding to mask pattern 25B2 of mask 25B in the backsurface of wafer 1W.

Thus, after applying binding material 8 to the back surface of wafer 1Wselectively, as shown in FIG. 50, mask 25B is removed like theEmbodiment 2. Then, a plurality of fine solid-like adhesive layers 8 care selectively formed on the back surface of wafer 1W by drying bindingmaterial 8 like the Embodiments 1 and 2. Here, as shown in FIG. 51, theplane area of adhesive layer 8 c is extremely smaller than the planearea of chip 1C. For this reason, since a big difference will not begenerated in the gross area of adhesive layer 8 c arranged in the regionof chip 1C even if the location of adhesive layer 8 c shifts a littlevertically and horizontally rather than the location which was beingplanned, the total adhesive strength of adhesive layer 8 c of the backsurface of chip 1C does not fall greatly, either. Since it is fine, andis isolated and each adhesive layer 8 c is mutually separated even ifthe location of adhesive layer 8 c shifted a little vertically andhorizontally rather than the location which was being planned andadhesive layer 8 c is arranged at cutting area CR of wafer 1W, it doesnot become the hindrance of cutting of wafer 1W. Therefore, the planealignment accuracy of mask 25B for forming adhesive layer 8 c and wafer1W can be eased.

Next, FIG. 52 shows the cross-sectional view of wafer 1W at the time ofwafer mounting step 102B3 of chip division step 102B. FIG. 53 shows thecross-sectional view of wafer 1W after WSS peeling process 102B4, andFIG. 54 shows the cross-sectional view of wafer 1W at the time ofdivision step 102B5.

At this step, as shown in FIG. 52, after sticking the back surface(formation surface of adhesive layer 8 c) of wafer 1W on tape 10 a ofjig 10, as shown in FIG. 53, like the Embodiments 1-4, supportingsubstrate 4 is peeled and adhesive layer 3 is continuously removed likethe Embodiments 1-4. Then, as shown in FIG. 54, wafer 1W is divided intoeach chip 1C like the Embodiment 1-4 by making reforming area PL ofwafer 1W into a division origin (stealth dicing). Since adhesive layer 8c is mutually separated by Embodiment 5 smaller than chip 1C at thistime, when cutting chip 1C, adhesive layer 8 c can also be separatedfinely. Therefore, since stealth dicing is employable, a semiconductordevice can be made thin. Since the external appearance failure of chip1C can be reduced, the yield of a semiconductor device can be improved.An effect which is the same as that of the Embodiments 1 and 2 can beacquired except this.

Since assembly process 102C after this is the same as the Embodiments 1and 2, explanation is omitted. In Embodiment 5, although the explanationis made using the flow of FIG. 1, the method explained by Embodiment 5is applicable also to the flow of FIG. 36.

Embodiment 6

FIG. 55 shows the cross-sectional view of the semiconductor device ofEmbodiment 6. In Embodiment 6, lower layer chip 18C is mounted on themain surface of wiring substrate 17 via bump electrode 30, where themain surface (device formation surface) is turned to the main surface ofwiring substrate 17. It electrically connects with the electrode on themain surface of wiring substrate 17 through bump electrode 30, and theintegrated circuit of chip 18C is electrically further connected to thewiring of wiring substrate 17. Bump electrode 30 includes, for examplelead (Pb)-tin (Sn) solder. Under-filling 31 is filled up between thefacing surfaces of chip 18C and wiring substrate 17.

Chip 1C is mounted on the back surface of chip 18C. The back surface ofchip 1C is adhered on the back surface of chip 18C via adhesive layer 8a. The integrated circuit of the main surface of chip 1C is electricallyconnected to electrode 17 a of wiring substrate 17 via wire 21 like theEmbodiment 1. The thickness of the above-mentioned adhesive layer 8 a issmaller than the distance between the facing surfaces of chip 18C andwiring substrate 17.

The mounting method of lower layer chip 18C is as follows, for example.First, chip 18C is transported to the chip mounting region of wiringsubstrate 17, after the main surface has turned to the bottom, andtemporary fixing of bump electrode 30 of the main surface of chip 18Cand the electrode of a main surface of wiring substrate 17 is made usingpaste material. Then, bump electrode 30 of chip 18C and the electrode ofwiring substrate 17 are adhered (flip chip bonding) by making reflowtreatment (heat treatment). Then, under-filling 31 is filled up betweenthe facing surfaces of chip 18C and wiring substrate 17. Since themounting method of the upper chip 1C is the same as the Embodiment 1,explanation is omitted. It is good also considering adhesive layer 8 aas adhesive layers 8 b and 8 c explained by the Embodiment 2, and 4 and5.

Embodiment 7

FIG. 56 shows the cross-sectional view of the semiconductor device ofEmbodiment 7. At Embodiment 7, on the main surface of chip 1C1 (1C),other chip 1C2 (1C) is mounted, where the main surface is turnedupwards. The back surface of chip 1C2 of the top layer is adhered on themain surface of chip 1C1 via adhesive layer 8 a. The integrated circuitof the main surface of chip 1C2 is electrically connected to electrode17 a of wiring substrate 17 via wire 21. Since adhesive layer 8 a of theback surface of chip 1C1 and 1C2 is formed thinly, the semiconductordevice which has the multi-stage structure of chip 18C, 1C1, and 1C2 canbe made into a thin shape. The thickness of adhesive layer 8 a of theback surface of chip 1C2 of the top layer is equal to the thickness ofadhesive layer 8 a of the back surface of an intermediate layer's chip1C1. By making equal thickness of adhesive layer 8 a of the back surfaceof respective chips 1C1 and 1C2, a thickness design of adhesive layer 8a of the back surface of respective chips 1C1 and 1C2 can be made easy.

Chip 18C of an undermost layer may be pasted up on the main surface ofwiring substrate 17 by adhesive layer 20 a like the Embodiment 1. Inthis case, the thickness of adhesive layer 20 a is thicker than adhesivelayer 8 a of the back surface of chip 1C1 and 1C2. Adhesive layer 8 a isreplaceable to adhesive layer 8 b or 8 c explained by the Embodiment 2,and 4 and 5.

Embodiment 8

FIG. 57 shows the cross-sectional view of the semiconductor device ofEmbodiment 8. The semiconductor device of Embodiment 8 is set to SIP(System In Package) by which the system of the desired function wasbuilt in one package. On the main surface of wiring substrate 17, aplurality of thin chips 18C, 1C, and 37C are laminated. Chip 18C of theundermost layer is mounted on the main surface of wiring substrate 17via bump electrode 30 of the main surface. Logic circuits, such as CPU(Central Processing Unit) and DSP (Digital Signal Processor), are formedin the main surface of this chip 18C, for example. On the back surfaceof this chip 18C, chip 1C is mounted via adhesive layer 8 a. Memorycircuits, such as SRAM (Static Random Access Memory) and a flash memory,are formed in the main surface of this chip 1C, for example. Pad 1LB ofthe main surface of this chip 1C is electrically connected withelectrode 17 a of the main surface of wiring substrate 17 via wire 21.On the main surface of this chip 1C, chip 37C is mounted via spacer 35and DAF 36. Memory circuits, such as SRAM and a flash memory, are formedin this chip 37C, for example, and the pad of the main surface of chip37C is electrically connected with electrode 17 a of the main surface ofwiring substrate 17 via wire 21. Such chips 18C, 1C, and 37C and wire 21are sealed by sealing body 22.

Chip 18C may be pasted up on the main surface of wiring substrate 17 byadhesive layer 20 a like the Embodiment 1. Adhesive layer 8 a isreplaceable to adhesive layer 8 b or 8 c explained by the Embodiment 2,and 4 and 5.

In the foregoing, the present invention accomplished by the presentinventors is concretely explained based on above embodiments, but thepresent invention is not limited by the above embodiments, butvariations and modifications may be made, of course, in various ways inthe limit that does not deviate from the gist of the invention.

Although mainly the case where invention made by the present inventorwas applied to the manufacturing method of the semiconductor devicewhich is the utilization field used as the background was explained inthe above explanation, it is not limited to it, but many things can beapplied, for example, it can be applied also to the manufacturing methodof a micromachine.

The present invention is applicable to the manufacturing industry of asemiconductor device.

1. A method of manufacturing a semiconductor device, comprising thesteps of: (a) providing a wiring substrate including a main surface, aplurality of wirings formed on the main surface, a plurality of firstelectrodes formed on the main surface, a back surface opposite to themain surface, and a plurality of second electrodes formed on the backsurface; (b) disposing a first adhesive material on the main surface ofthe wiring substrate; (c) after the step (b), mounting a firstsemiconductor chip over the main surface of the wiring substrate via thefirst adhesive material such that a first rear surface of the firstsemiconductor chip faces the main surface of the wiring substrate, andsuch that the wirings formed on the main surface of the wiring substrateare overlapped with the first semiconductor chip via the first adhesivematerial, and whereby a part of the first adhesive material isoverflowed from a first side surface of the first semiconductor chip ina cross-sectional view, and whereby a part of the first side surface ofthe first semiconductor chip is covered with the part of the firstadhesive material, the first semiconductor chip including a first frontsurface, a plurality of first bonding pads formed on the first frontsurface, the first rear surface opposite to the first front surface, andthe first side surface located between the first front surface and thefirst rear surface; (d) after the step (c), stacking a secondsemiconductor chip over the first front surface of the firstsemiconductor chip via a second adhesive material formed on a secondrear surface of the second semiconductor chip, such that the second rearsurface of the second semiconductor chip faces the first front surfaceof the first semiconductor chip, and such that an entirety of the secondsemiconductor chip is located inside the first bonding pads, the secondsemiconductor chip including a second front surface, a plurality ofsecond bonding pads formed on the second front surface, the second rearsurface opposite to the second front surface, and a second side surfacelocated between the second front surface and the second rear surface;wherein the second semiconductor chip is formed by following steps(d1)-(d3), (d1) providing a semiconductor wafer having a third frontsurface, and a third rear surface opposite to the third front surface;(d2) forming an adhesive layer on the third rear surface of thesemiconductor wafer; and (d3) cutting the semiconductor wafer and theadhesive layer, whereby the second semiconductor chip having the secondadhesive material formed on the second rear surface is obtained; and (e)sealing the first semiconductor chip and the second semiconductor chipwith a resin; wherein a thickness of the second adhesive material isthinner than a thickness of the first adhesive material located directlyunder the first semiconductor chip.
 2. The method according to claim 1,further including providing the main surface of the wiring substrate tohave a greater surface irregularity as compared to a surfaceirregularity of the first front surface of the first semiconductor chip.3. The method according to claim 1, further including forming the secondadhesive material using a spin coating method.
 4. The method accordingto claim 1, further including disposing a paste-like material as thefirst adhesive material on the main surface of the wiring substrate. 5.The method according to claim 1, further including after the step (d)and before the step (e), electrically connecting one of the firstbonding pads of the first semiconductor chip with one of the firstelectrodes of the wiring substrate via a wire.
 6. The method accordingto claim 1, further including after the step (d) and before the step(e), electrically connecting one of the second bonding pads of thesecond semiconductor chip with one of the first bonding pads of thefirst semiconductor chip via a wire.
 7. The method according to claim 1,further including forming the second adhesive material on the secondrear surface of the second semiconductor chip to have a thickness thatis less than 10 μm.
 8. The method according to claim 7, furtherincluding forming the second adhesive material on the second rearsurface of the second semiconductor chip to have a thickness that isless than or equal to 5 μm.
 9. The method according to claim 1, furtherincluding disposing the first adhesive material on the main surface ofthe wiring substrate to have a thickness that is greater than or equalto 10 μm.